Field of the Disclosure
The present invention relates generally to power converters. More specifically, examples of the present invention are related to lighting systems including dimming circuitry.
Background
Electronic devices use power to operate. Power is generally delivered through a wall socket as high voltage alternating current (ac). A device typically referred to as a power converter can be utilized in lighting systems to convert the high voltage ac input into a well regulated direct current (dc) output through an energy transfer element. Switched mode power converters are commonly used to power many of today's electronics due to their high efficiency, small size, and low weight. During operation, a switch included in the power converter is used to provide the desired output by varying (1) the duty cycle (the ratio of the on time of the switch to the total switching period), (2) the switching frequency, or (3) the number of pulses per-unit-time of the switch.
In one type of dimming for lighting applications, a dimmer circuit disconnects a portion of the ac input voltage to limit the amount of voltage and current supplied to an incandescent lamp. This is generally known as phase dimming because it is often convenient to designate the position of the missing voltage in terms of a fraction of the ac input voltage (as measured in degrees). In general, the ac input voltage is a sinusoidal waveform and the period of the ac input voltage is referred to as a full line cycle.
While phase dimming may work well in some applications (for example, with incandescent lamps), in other applications, phase dimming may be less desirable due to the stringent power requirements of modern electronic devices.
Corresponding reference characters indicate corresponding components throughout the several views of the drawings. Skilled artisans will appreciate that elements in the figures are illustrated for simplicity and clarity and have not necessarily been drawn to scale. For example, the dimensions of some of the elements in the figures may be exaggerated relative to other elements to help to improve understanding of various embodiments of the present invention. Also, common but well-understood elements that are useful or necessary in a commercially feasible embodiment are often not depicted in order to facilitate a less obstructed view of these various embodiments of the present invention.